Method for manufacturing air filled packing cushions

ABSTRACT

A machine ( 1 ) for the production of packaging material in the form of air filled cushions ( 24 ) comprises feeding rollers ( 2 ) for conveying parallel two films of plastic material ( 20   a  and  20   b ), unwound starting from rolls ( 30   a  and  30   b ), according to a conveying direction. Downstream of the feeding rollers ( 2 ) air is supplied between the two films ( 20   a  and  20   b ) by means of a plurality of tubes ( 6 ) extending from a collector ( 5 ) and parallel to the conveying direction of the films ( 20   a  and  20   b ). Each tube ( 6 ) extends between two longitudinal heatsealing elements ( 10 ), crosses a couple of dragging rollers ( 8 ) and ends at transversal heat-sealing elements ( 15 ).

This application is a filing under 35 USC 371 of PCT/IB2004/001435 filedFeb. 16, 2004.

FIELD OF THE INVENTION

The present invention relates to the field of machines for theproduction of shock protecting material used for packaging and inparticular it relates to a method for welding thermically such materialin the form of air filled cushions during the production processthereof.

Furthermore, the invention relates to an apparatus that carries out thismethod.

DESCRIPTION OF THE PRIOR ART

As known, common packaging material comprise polystyrene foam, thepolyurethane foam, polystyrene foam balls, etc.

However, such packaging material adds a not negligible weight to thefinal load and scatters when extracting the packaged objects. Therefore,in certain cases “cushions” of plastic films are preferred as shockprotecting material, usually made of high density polyethylene havinghigh mechanical resistance with respect to other plastic materials, airfilled and used both for wrapping the transported objects and forblocking them in a container.

In the production of such cushions two films of high densitypolyethylene are unwound starting from rolls and coupled proceedingalong a certain direction. Then, they are firstly welded along spacedlongitudinal sealing lines, parallel to the direction of movement anddefining tubular chambers. Then, in the tubular chambers, during themovement, air is blown which remains trapped therein after that twospaced couples are made of transversal sealing lines close to eachother, orthogonal to the previous, obtaining closed cushions.

Both the longitudinal and the transversal sealing lines are made heatinglocally the polyethylene films by means of electrical resistance, orother heating source, which causes the films to soften locally and thento bind with each other. Furthermore, associated to the electricalresistances that are used for making each couple of transversal sealinglines, a blade is usually arranged suitable for cutting between thesealing lines, forming downstream an array of air filled cushionsseparated from the upstream ones still being formed; alternatively, theblade can make a tear line, that can be broken in a second time by anuser.

In particular, the blade works simultaneously to the electricalresistance that makes the couple of transversal sealing lines;therefore, to switch between cut and tear line it is necessary to stopthe machine, to disassemble the blade and change it or to set itsposition, and then to start again the process with relevant loss oftime.

Another drawback of the prior art machines is that both the longitudinaland the transversal sealing lines are made at the same time by a samemechanism. Therefore, it is possible to change shape and size of thecushions only changing the speed of the films of plastic material withinpredetermined limits.

Furthermore, in the prior art machines the systems that hold theelectrical resistances, or other heating devices, are not capable ofapplying high forces onto the polyethylene films. Therefore, arelatively long time is necessary for local heating the polyethylenefilms and causing it to soften in order to allow binding. All thisstrongly limits the speed of the production process.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a machinefor the production of packaging material in the form of cushions filledof air or other gas that allows an easy adjustment of the shape and thesize of the cushions.

It is a first particular object of the invention to provide such amachine that allows to make tearing lines or cuts without any particularadjustment means.

It is a second particular object of the invention to provide such amachine that can work at high production rate.

It is another particular object of the invention to provide a method forthe production of packaging material in the form of cushions filled ofair or other gas capable of overcoming the drawbacks of the prior art.

A first aspect of the invention relates to a machine for the productionof packaging material in the form of cushions filled with air or othergas comprising:

-   -   means for feeding parallel to each other in a conveying        direction two films of plastic material;    -   means for blowing air or other gas in ducts arranged between the        two films of plastic material;    -   means for making longitudinal sealing lines on said films to        define tubular chambers in which air is blown through said        ducts;    -   means for making on said films a couple of transversal sealing        lines close to each other in order to form, substantially,        cushions containing a certain amount of air, or other gas,        trapped between two adjacent longitudinal sealing lines and two        consecutive couples of transversal sealing lines close to each        other;    -   means for cutting orthogonally said cushions between each couple        of transversal sealing lines close to each other;        whose main feature is that said means for cutting are movable        towards/away from said cushions operated by at least one        actuator, wherein said or each actuator is capable of moving        selectively said means for cutting according to either a stroke        for making a tear line or a stroke for making a complete cut.

Advantageously, said actuator, or said first actuator, for moving saidmeans for cutting is associated to at least one second actuator. Thisway, it is possible to make a transversal tear line by operating onlythe first actuator or, alternatively, to make a cut for separating twoconsecutive cushions by operating at the same time the first and thesecond actuator.

Preferably, the means for cutting comprise a toothed blade havingtriangular teeth, whereby when making a tear line only the tips of theteeth penetrate the films of plastic material, whereas when making afull cut the teeth penetrate completely the films.

Preferably, the means for making said longitudinal sealing lines areoperated by at least one actuator independent from the actuator of themeans for making said transversal sealing lines, so that it is possibleto adjust the size of the cushions by operating the respective actuatorsin a predetermined way.

Advantageously, said means for making said transversal sealing lines aretwo heat-sealing elements that act orthogonally to the films of plasticmaterial, comprising electrical resistances suitable for heating saidfilms up to causing it to partially melt and then to bind to each other.Such heat-sealing elements are associated to a toothed blade slidinglyarranged between them. In particular, each heat-sealing element consistsin a movable bar, movable orthogonally towards/away from the films ofplastic material, and in a fixed bar that is located on the other sidewith respect to the film.

Preferably, the or each actuator is of pneumatic type.

The packaging material obtained by the machine as above described can bestored as single cushions or rows of cushions in boxes or bags, or woundinto rolls. In the latter case, a support is provided equipped with areel shaft brought into rotation by a motor for causing the cushions tobe rolled about it at the outlet of the machine.

In particular, the support can be operatively connected by a stiff linkto a basement on which the machine is mounted in order to avoid thatwhen rolling the support same is displaced from a correct position. Themotor that operates the reel shaft can be, furthermore, electricallyconnected to an electronics that operates the machine. This allows toturn on or off the motor according to the operative conditions thatoccur during the production of cushions.

Furthermore, means can be provided for testing the correct rolling ofsaid cushions on said reel shaft comprising optical sensors that detectthe presence of a loop along the web being rolled up. More in detail,the optical sensors are suitable for turning on or off the motor if theshape and or the size of the loop do not fall within determined values.

According to another aspect of the invention, a method for theproduction of packaging material in the form of air filled cushions, orother gas comprises the steps of:

-   -   feeding in parallel according to a conveying direction two films        of plastic material;    -   blowing air or other gas in parallel ducts between the two films        of plastic material;    -   making longitudinal sealing lines on said films to define        tubular chambers in which air is blown through said ducts;    -   making couples of transversal sealing lines close to each other        on said films in order to form substantially cushions containing        a certain amount of air, or other gas, trapped between two        adjacent longitudinal sealing lines and two consecutive couples        of transversal sealing lines close to each other;    -   cutting orthogonal to said cushions between two consecutive        couples of transversal sealing lines close to each other,        whose main feature is that said step of cutting is made through        means for cutting movable towards/away from said cushions        operated by at least one actuator capable of moving selectively        said means for cutting according to either a stroke for making a        tear line or a stroke for making a complete cut.

In particular, the step of making transversal sealing lines is carriedout by two heat-sealing elements, which act orthogonally to said filmsof plastic material, between which a toothed blade is slidingly arrangedhaving triangular teeth. Each heat-sealing element consists in barsmovable orthogonally to the cushions and in fixed bars arranged on theother side with respect to the films of plastic material. Therefore, formaking the transversal sealing lines of the air filled cushions, themovable bars, operated by an actuator, approach the surface of thetubular chamber, squeeze it against the fixed bars, and make thetransversal sealing lines for partially melting, or heat-sealing, theplastic material. Then, the toothed blade arranged between the two fixedbars translates orthogonally to the plane of the cushions for a cuttingstep that, according to the case, can be of making a tear line or acomplete cut.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be made clearer with the following description of anembodiment thereof, exemplifying but not limitative, with reference toattached drawings wherein:

FIG. 1 shows a perspective view of a machine for the production ofpackaging material in the form of cushions filled with air, or othergas, according to the invention;

FIG. 2 shows a cross sectional view of the machine of FIG. 1 accordingto arrows II-II;

FIG. 3 shows diagrammatically a longitudinal cross section of themachine of FIG. 1;

FIG. 4 shows a cross sectional view of the machine of FIG. 1 accordingto arrows IV-IV;

FIGS. 5 and 6 show respectively a cross sectional view of and a top planview of the machine of FIG. 1 in the case of making a tear-out line;

FIGS. 7 and 8 show respectively a cross sectional view of and a top planview of the machine of FIG. 1 in the case of making a complete cut;

FIGS. from 9 to 11 show diagrammatically a cross sectional view of therelative positions of the toothed blade and of the films of plasticmaterial respectively in case of return position, making a tear line andmaking a complete cut;

FIGS. from 12 to 14 show diagrammatically a cross sectional view of therelative positions of the blade and of the transversal heat-sealingelements, respectively in case of return position, making a tear lineand making a complete cut;

FIG. 15 shows diagrammatically an elevational side view of the machineof FIG. 1 connected to a rolling support of the packaging material.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1 and 3, a machine 1 for the production ofpackaging material in the form of air filled cushions 24 (FIG. 6),according to the invention, comprises feeding rollers 2 for conveyingtwo films of plastic material 20 a and 20 b parallel to each other,unreeled from rolls 30 a and 30 b, according to a direction of movementas indicated in the figure by the arrows. Downstream of the feedingrollers 2 there is a collector 5 to which air is supplied. The air isthen blown in the space between the two films 20 a and 20 b by means ofa plurality of tubes 6 pneumatically connected to collector 5 andparallel to the conveying direction of films 20 a and 20 b. Each tube 6extends between two heat-sealing elements 10 suitable for makinglongitudinal sealing lines 21 onto films 20 a and 20 b (FIG. 2). Thisway, tubular chambers 23 are formed in which a certain amount of air ispresent.

Then, tubular chambers 23 thus formed pass through a couple of draggingrollers 8 on whose surface a plurality is provided of circumferentialgrooves, not shown, through which tubes 6 pass. This allows tubes 6 toend at heat-sealing elements 15, which are suitable for making a coupleof transversal sealing lines close to each other 22 on films 20 a and 20b. Such transversal sealing lines 22 transform tubular chambers 23 intoair filled cushions 24 (FIG. 6).

Each heat-sealing element 10, or 15, consists in a fixed bar 10 a, or 15a, and in a movable bar 10 b, or 15 b, arranged orthogonally to thefilms of plastic material, and at opposite sides with respect to thefilms. In particular, the movable bars 10 b are mounted on a support 12allowing it to move towards/away from the films by means of actuators11. Similarly, movable bars 15 b are mounted on a support 14 operated byactuators 16.

Between fixed bars 15 b a toothed blade is mounted 17, with triangularteeth 16, movable towards/away from the cushions 24 by means of twocouples of pneumatic actuators 18 a and 18 b operatively connected tothe ends of blade 17.

Such embodiment allows a cutting step of the films of plastic material,according to the case, making a tear line 25 (FIG. 6) or making a fullcut (FIG. 8).

In particular, to make a tear line 25 (FIGS. 5 and 6) compressed air isfed to only pneumatic actuators 18 a, so that the respective stems movevertically up to bringing the blade 17 from a starting position externalto films 20 (FIG. 9) to a position in which teeth 16 pierce films 20 upto only a part of their height (FIG. 10).

In the case, instead, a full cut (FIGS. 7 and 8) is requested compressedair is fed both to actuators 18 a and to actuators 18 b. Therefore, thestems of actuators 18 b move vertically in a direction opposite to films20 and pushing against a casing of a guide 19 causing actuators 18 a and18 b to slide within guide 19 same (FIG. 11). This allows blade 17 tolower for a full cut of films 20.

As shown in detail in a cross sectional view of FIGS. from 12 to 14, thechoice of two couples of actuators 18 a and 18 b as above describedallows to make a tear line 25 or a full cut continuously withoutstopping the machine.

The packaging material obtained by the machine 1 can be stored in theform of single cushions 24, or rows of cushions 24, or rolls 65 (FIG.15). In the latter case, the rolls 65 are wound by means of a motor 70about a reel shaft mounted on support 60.

To prevent support 60 from being displaced from a correct position whenforming roll 65, a stiff link 62 connects it to a basement 50 on whichthe machine is mounted 1. The support is easily freed/locked byreleasable lock means.

Motor 70 can be, furthermore, connected to an electronics that operatesthe machine 1 by means of an electrical cable 71. This way, theelectronics that operates the machine 1 can operate the stop of motor 70if problems arise when making roll 65.

The machine 1 can be, furthermore, provided with optical sensors 80 fortesting when rolling is carried out correctly. This can be executedcontrolling determined parameters of the process, for example, the shapeand the size of a loop 30 along the web of product being rolled up 65.

More in detail if optical sensors 80 verify that loop 30 has apredetermined shape and size, electric power is supplied to motor 70 ofsupport 60. If instead, the shape and the size of the loop 30 is notwithin predetermined values, for example, because the roll winding speedis too high and then the rolling power is too high, to avoid that theproduct is damaged the delivery of electric power to the motor 70 andthen winding roll 65 on support 60 is discontinued. This avoids damagesto the packaging material, owing to possible jamming or tearing causedby lack of synchronism between the rolling speed of roll 65 and theproduction of the web of air filled cushions 24 from machine 1.

The foregoing description of a specific embodiment will so fully revealthe invention according to the conceptual point of view, so that others,by applying current knowledge, will be able to modify and/or adapt forvarious applications such an embodiment without further research andwithout parting from the invention, and it is therefore to be understoodthat such adaptations and modifications will have to be considered asequivalent to the specific embodiment. The means and the materials torealise the different functions described herein could have a differentnature without, for this reason, departing from the field of theinvention. It is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

1. Method for the production of packaging material in the form oftubular cushions filled with air, or other gas, comprising the steps of:feeding in parallel in a conveying direction two films of plasticmaterial; blowing air or other gas in parallel ducts between said filmsof plastic material; making longitudinal sealing lines on said films todefine tubular chambers in which air is blown by said ducts, and makingon said films couples of transversal sealing lines close to each otherin order to substantially form cushions containing a certain amount ofair or other gas; and outputting a row of tubular cushions containing apredetermined amount of air or other gas trapped between two adjacentlongitudinal sealing lines and two consecutive couples of transversalsealing lines close to each other, wherein when making a couple oftransversal sealing lines close to each other, a step is provided oforthogonally moving a cutting means between said transversal sealinglines close to each other, and wherein said step of orthogonally movingsaid cutting means is made by at least one actuator capable ofselectively moving said cutting means according to either a stroke formaking a tear line or a stroke for making a complete cut, such thatadjacent cushions of said row are connected at said transversal sealinglines by a transversal tear line and other adjacent cushions of said roware separated from each other at said transversal sealing lines y atransversal complete cut.
 2. Method according to claim 1, wherein saidstep of cutting is made by causing a toothed blade arranged betweenfixed bars to move orthogonally to said films of plastic material andmaking, selectively, a tear line or a complete cut.
 3. Method accordingto claim 1, wherein the step of cutting is made by a first actuator thatis associated with a second actuator, such that said stroke for making atear line is obtained by operation of said first actuator, and saidstroke for making a complete cut is obtained by said first actuator andsaid second actuator operated at the same time.